Construction crews unearthed the burial chamber this spring near the town of Tula, the ancient Toltec capital, 50 miles (80 kilometers) north of Mexico City (see Mexico map).

The chamber contained 24 skeletons of children believed to have been sacrificed between A.D. 950 and 1150, according to Luis Gamboa, an archaeologist at Mexico's National Institute of Anthropology and History.

All but one of the children were between 5 to 15 years of age, and they were likely killed as an offering to the Toltec rain god Tlaloc, Gamboa said.

The Toltec, a pre-Aztec civilization that thrived from the 10th to 12th centuries, had not been previously thought to have sacrificed children.

But the ritualistic placement of the skeletons, cut marks on bones, and the presence of a figurine of Tlaloc led Gamboa to conclude the children had been sacrificed to bring rain.

"To try and explain why there are 24 bodies grouped in the same place, well, the only way is to think that there was a human sacrifice," Gamboa told the Reuters news agency.

"You can see evidence of incisions, which make us think they possibly used sharp-edged instruments to decapitate them."

Elaborate Burials

The skeletons were each found in a seated position looking east to face the sunrise, Gamboa said.

Several artifacts were also found around the bodies, some of which suggest that the children had been brought in from another region, he added.